Drill bits and methods for forming curved portions of a borehole

ABSTRACT

Drill bits and methods for forming a curved portion of a borehole include a first plurality of cutting elements, such as tungsten carbide inserts, positioned at the outer or perimeter region of a bit face and oriented to bore in a direction generally perpendicular to the bit face. A second plurality of cutting elements, such as polycrystalline diamond compact cutters, are positioned at the inner region of the bit face and oriented to bore in a direction generally parallel to the bit face. When forming a curved portion of a borehole, the first plurality of cutting elements engage the formation to allow the drill bit to reorient at sharper angles than conventional methods for forming a curve, while when forming a linear portion of a borehole, the second plurality of cutting elements engage the formation to provide stability to the drill bit and a rapid rate of penetration.

FIELD

Embodiments usable within the scope of the present disclosure relate,generally, to drill bits and methods of forming boreholes, and morespecifically, to drill bits and methods for forming boreholes having oneor more curved regions.

BACKGROUND

Directional drilling is commonly performed both to increase productionof a single well (e.g., by providing bores at multiple angles to betterreach one or multiple producing regions of a formation), and to minimizethe environmental impact and/or surface area of such wells. Horizontaldrilling is especially useful for increasing the productivity of a well,by as much as twenty times that of a vertical well, or more, byextending a substantial portion of the wellbore horizontally, through aproducing layer of the formation.

While some types of non-vertical wells can be drilled simply byorienting the drill bit at a non-vertical angle (e.g., slant drilling),most modern directional drilling operations utilize a bent member,positioned near the drill bit, in conjunction with a downhole steerablemud motor. When the drill string is not rotating (e.g., when fluid ispumped through the mud motor), the bent portion of the string moves todirect the drill bit in a different direction. Then, once the drill bitreaches the desired angle, the drill string is permitted to rotate,causing the drill bit to bore in the selected direction.

Depending on the characteristics of a formation and the desired shape ofa borehole, the most time consuming and difficult aspect of directionaldrilling normally involves “building a curve” in a directional borehole.Sometimes, multiple drilling operations are necessary, in which thedrill string is removed, such that a different bent member, mud motor,and/or drill bit can be used for each portion of a curve as the angle ofthe borehole changes. A typical curve in a borehole can be formed usinga member and/or a motor having a two-degree bend therein (e.g., a memberthat will change the orientation of the drill bit by two degrees forevery 100 feet drilled), the angle being limited by the length andcapabilities of the drill bit, the conduit used within the wellbore, andother similar factors. As such, a curved portion of a well can oftenhave a substantial length and require a significant quantity of time andlabor to form.

A need exists for drill bits and methods capable of rapidly building acurve in borehole, during a single trip, having a faster rate ofpenetration than conventional drill bits and methods.

A need also exists for drill bits capable of forming curves in aborehole at an angle greater than conventional drill bits and methods,thus shortening the length of a curved portion of a borehole as well asthe time required to build the curve.

Embodiments usable within the scope of the present disclosure meet theseneeds.

SUMMARY

Embodiments usable within the scope of the present disclosure includedrill bits adapted for stably and efficiently forming a curved regionwithin a borehole. The drill bit can include a body, adapted for anydesired borehole size, formed from steel, tungsten carbide matrix, orother similar materials known in the art, depending on the nature of theformation and the desired structural characteristics of the drill bit.The body can include a shank disposed at a first end (e.g., forthreading and/or otherwise attaching to a drillstring or adjacentcomponents), and a bit face disposed at a second end.

The bit face can include an outer portion and an inner portion. Itshould be understood that this division of the bit face into suchportions is primarily conceptual, and that the bit face may or may notinclude separate or integral members or any physical or visibledelineation between the outer and inner portions thereof. For example,in an embodiment, the “outer portion” of the bit face can include theperimeter thereof, and a portion of the bit face adjacent andimmediately interior of the perimeter, while the “inner portion” caninclude the remainder of the bit face located interior of the outerportion (e.g., toward the center of the drill bit).

A first plurality of cutters can be positioned in the outer portion ofthe bit face, while a second plurality of cutters can be positioned inthe inner portion. The first plurality of cutters can be oriented tobore into a formation in a direction generally perpendicular to the bitface (e.g., ahead of the drill bit by crushing and/or otherwisepenetrating into the formation). The second plurality of cutters can beoriented to bore into a formation in a direction generally parallel tothe bit face (e.g., ahead of the drill bit by cutting, shaving, and/orslicing into the formation in an at least partially lateral directionrelative to the axis of the drill bit). In an embodiment, the firstplurality of cutters can include tungsten carbide insert (TCI) cuttingstructures, while the second plurality of cutters can includepolycrystalline diamond compact (PDC) cutting elements.

Conventionally, tungsten carbide inserts are primarily used in the gageregion of a drill bit (e.g., tungsten carbide “buttons”) to maintain thegage of a borehole, prevent wear on other portions of the drill bit,prevent wobbling and/or instability of the drill bit during operation.Tungsten carbide inserts are also used in roller cone bits (e.g., rockbits). Use of tungsten carbide inserts in place of PDC cutters on thebit face of a drill bit (e.g., on the outer/perimeter region of the bitface) would generally be expected to provide an inefficient rate ofpenetration due to the limited cut formed by the tungsten carbideinserts. However, in embodiments of the present invention, the firstplurality of cutters (e.g., tungsten carbide inserts) defines a leadingedge adapted to engage the formation when forming a curved region of aborehole, while the second plurality of cutters (e.g., polycrystallinediamond compact cutters) are adapted to engage the formation whenforming a linear region of the borehole. Thus, when the drill bit isurged laterally and/or otherwise manipulated to cause a curve in thepath of the borehole, the first plurality of cutters, disposed on theouter portion of the bit face, define a leading edge that performs themajority of the boring responsible for extending the borehole along acurved path. For example, while boring along a curved path, a pluralityof tungsten carbide inserts on the outer portion of the bit face can beused to form limited cuts in the formation, while a plurality ofpolycrystalline diamond compact cutting elements can form larger cutsonce the inner portion of the bit face contacts the formation, thusfacilitating travel of the drill bit along the curved path. Whenextending the borehole in a linear direction, the second plurality ofcutters, disposed on the inner portion of the bit face, can perform themajority of the boring responsible for extending the borehole.

In an embodiment, the inner portion of the bit face can have a recessedregion (e.g., a recessed cone shape). While the height/depth of thisrecessed region can vary depending on the nature of the formation andthe desired structural characteristics of the drill bit, in a preferredembodiment, the height of the recessed region can be about four inches.During drilling operations, portions of the formation in front of thebit face, that are not contacted by the first plurality of cutters onthe outer portion thereof, can form a “stump” that enters the recessedregion. Contact between the bit face and the stump can promote stabilityof the drill bit and prevent undesired deviation of the drill bit fromthe current direction of boring. As the second plurality of cutterscontact the stump, the stump can be efficiently drilled through due tothe orientation and/or nature of the second plurality of cutters.

Embodiments of the present drill bit and related methods possess anenhanced rate of penetration (e.g., 200 feet per hour) over conventionalPDC drill bits when forming a curved portion of a borehole, reducing thedrilling time required to form a curve in a horizontal well by as muchas eight to ten hours, or more. Further, embodiments of the presentdrill bit and method can form curves at an angle of as great as thirtyfive degrees, or more, though during normal operations, a curve ofeighteen degrees is desirable to accommodate most types of boreholeconduits. In an embodiment, the present drill bit can build a curve atan angle ranging from thirteen to twenty degrees. For example, the drillbit can drill a curve that changes direction at a rate of thirteendegrees per 100 feet drilled. In contrast, conventional curved portionsof a borehole are typically formed using a bent member and/or motorhaving a two-degree bend. In other embodiments, the drill bit can beadapted to form a curve ranging from eight degrees to twelve degrees. Infurther embodiments, a drill can be adapted to form a curve ranging fromeight degrees to thirty-five degrees.

To further facilitate travel of the drill bit along a sharper curvedpath, the overall length of the drill bit can be limited. For example,embodiments of drill bits can include a borehole gage ranging from 0.5inches to 2 inches, with an 8.75 drill bit having a make up length ofabout 8 inches, when measured from the base of the shank to the front ofthe bit face, and a 6.5 inch drill bit having a make up length of about5.75 inches. In a preferred embodiment, the overall length of the drillbit can be five inches or less. Use of a comparatively short drill bitpositions the bit face closer to the motor than conventional drill bits,further enhancing the ability of the present drill bit to make sharpturns during boring.

While configurations of cutters on the bit face can be varied, dependingon the nature of the formation and the desired structuralcharacteristics of the drill bit, in an embodiment, the bit face caninclude a plurality of blades extending therefrom, with the secondplurality of cutters positioned along an inner portion of the blades(e.g., toward the center of the bit face), while the first plurality ofcutters are positioned along an outer portion of the blades and/orbetween individual blades. In further embodiments, the bit face caninclude a port positioned at the approximate center thereof for washingone or more of the cutters on the bit face.

Embodiments usable within the scope of the present disclosure therebyprovide drill bits and methods capable of rapidly building a curve in aborehole, during a single trip, having a faster rate of penetration thanconventional drill bits and methods, and/or a sharper curve than what isattainable using conventional means, thereby enabling faster and morereliable formation of curved portions of boreholes by shortening thelength thereof and the time required to form such a curve.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of various embodiments usable within thescope of the present disclosure, presented below, reference is made tothe accompanying drawings, in which:

FIG. 1 depicts a side view of an embodiment of a drill bit usable withinthe scope of the present disclosure.

FIG. 2 depicts a front view of the drill bit of FIG. 1, showing anembodiment of the bit face thereof.

FIG. 3 depicts a perspective view of the drill bit of FIG. 1.

One or more embodiments are described below with reference to the listedFigures.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Before describing selected embodiments of the present disclosure indetail, it is to be understood that the present invention is not limitedto the particular embodiments described herein. The disclosure anddescription herein is illustrative and explanatory of one or morepresently preferred embodiments and variations thereof, and it will beappreciated by those skilled in the art that various changes in thedesign, organization, means of operation, structures and location,methodology, and use of mechanical equivalents may be made withoutdeparting from the spirit of the invention.

As well, it should be understood that the drawings are intended toillustrate and plainly disclose presently preferred embodiments to oneof skill in the art, but are not intended to be manufacturing leveldrawings or renditions of final products and may include simplifiedconceptual views to facilitate understanding or explanation. As well,the relative size and arrangement of the components may differ from thatshown and still operate within the spirit of the invention.

Moreover, it will be understood that various directions such as “upper”,“lower”, “bottom”, “top”, “left”, “right”, and so forth are made onlywith respect to explanation in conjunction with the drawings, and thatcomponents may be oriented differently, for instance, duringtransportation and manufacturing as well as operation. Because manyvarying and different embodiments may be made within the scope of theconcept(s) herein taught, and because many modifications may be made inthe embodiments described herein, it is to be understood that thedetails herein are to be interpreted as illustrative and non-limiting.

Embodiments usable within the scope of the present disclosure relate todrill bits and methods adapted for forming a curved portion of aborehole more efficiently than conventional drill bits and methods. Forexample, an embodied drill bit can include a first plurality of cutters(e.g., tungsten carbide inserts) positioned on the outer (e.g,perimeter) portion of the bit face and oriented to bore perpendicular to(e.g., in front of and in a direction out from) the bit face, and asecond plurality of cutters (e.g., polycrystalline diamond compactcutters) positioned on the inner portion (e.g., within a recessedconical region) of the bit face and oriented to bore parallel to (e.g.,in front of and in a direction along) the bit face.

Referring now to FIG. 1, a diagrammatic side view of an embodiment of adrill bit (10) usable within the scope of the present disclosure isshown. The depicted drill bit (10) includes a body (12) having a shank(14) disposed at an end thereof, and a bit face (16) disposed at anopposing end. The body (12) can be formed from steel, tungsten carbidematrix materials, and/or other similar materials known in the art,depending on the characteristics of the formation within which the drillbit (10) will be used to form a borehole and/or the desired structuralcharacteristics of the drill bit (10) (e.g., resistance to and/ordissipation of temperature, resistance to pressure, ability to withstandshock and/or vibration, etc.). The shank (14) can be formed from steelor other similar materials, and is shown having a pin shape, upon whichthreads can be formed for engagement with a conduit or an adjacentcomponent. Other methods of connection to adjacent conduits and/orcomponents, as known in the art, can be used in place of, or in additionto, the shank (14) without departing from the scope of the presentdisclosure. FIG. 1 depicts the bit face (16) having a plurality ofblades and cutting elements thereon and a recessed conical region (44)at the approximate center thereof.

Referring now to FIG. 2, a front view of the drill bit of FIG. 1 isshown, such that the bit face (16) can be visualized in greater detail.While embodiments of the present drill bit can include any configurationof blades and/or cutting elements, depending on the desired performanceof the drill bit, the nature of the formation, and/or other similarfactors, FIG. 2 depicts an exemplary embodiment in which the bit face(16) includes three primary blades (18A, 18B, 18C) extending therefrom.Each primary blade (18A, 18B, 18C) extends from the center of the bitface (16) to the edge thereof, then a distance along the side of the bitface (16), as shown in FIGS. 1 and 3. Each primary blade (18A, 18B, 18C)is shown having a plurality of tungsten carbide insert cutting elementson an outer portion thereof (e.g., along the perimeter of the bit face(16) and/or along the side thereof). For example, tungsten carbideinserts (24) on the front portion of the bit face (16) and a tungstencarbide insert (26) along the side of the bit face (16), on the secondprimary blade (18B) are labeled for reference. Each primary blade (18A,18B, 18C) is further shown having a plurality of polycrystalline diamondcompact cutting elements on an inner portion thereof, of which apolycrystalline diamond compact cutting element (28) on the secondprimary blade (18B) is labeled for reference. It should be understoodthat the specific number and placement of cutting elements on theprimary blades (18A, 18B, 18C) can vary depending on the desiredcharacteristics of the drill bit (10). For example, for illustrativepurposes, FIG. 2 depicts the first primary blade (18A) having fourpolycrystalline diamond compact cutting elements and two tungstencarbide insert cutting elements thereon, while the other primary blades(18B, 18C) are shown having three polycrystalline diamond compactcutting elements and three tungsten carbide insert cutting elementsthereon.

FIG. 2 further depicts there secondary blades (20A, 20B, 20C), shownequidistantly spaced between the primary blades (18A, 18B, 18C), thesecondary blades (20A, 20B, 20C) having a length extending along theside and outer portion (e.g., perimeter) of the bit face (16), andapproximately one-half the distance from the outer portion of the bitface (16) to the center thereof. Each secondary blade (20A, 20B, 20C) isshown having tungsten carbide insert cutting elements along the outerportions thereof. For example, tungsten carbide inserts (30) on thefront portion of the bit face (16) and a tungsten carbide insert (32)along the side of the bit face (16), on the third secondary blade (20C)are labeled for reference. Each secondary blade (20A, 20B, 20C) isfurther shown having polycrystalline diamond compact cutting elements onan inner portion thereof, of which a polycrystalline diamond compactcutting element (34) on the third secondary blade (20C) is labeled forreference. It should be understood that the specific number andplacement of cutting elements on the secondary blades (20A, 20B, 20C)can vary depending on the desired characteristics of the drill bit (10).For example, for illustrative purposes, FIG. 2 depicts the secondsecondary blade (20B) having two tungsten carbide inserts and twopolycrystalline diamond compact cutting elements thereon, while theother secondary blades (20A, 20C) have three tungsten carbide insertsand two polycrystalline diamond compact cutting elements thereon.

FIG. 2 also depicts six tertiary blades (22A, 22B, 22C, 22D, 22E, 22F)equidistantly spaced between the primary and secondary blades (18A, 18B,18C, 20A, 20B, 20C). Each of the tertiary blades (22A, 22B, 22C, 22D,22E, 22F) is shown having a generally short length, extending along theside and outer portion of the bit face (16), but not extending throughthe inner portion thereof. As such, each tertiary blade (22A, 22B, 22C,22D, 22E, 22F) is shown having tungsten carbide insert cutting elementsthereon, but lacks any polycrystalline diamond compact cutting elements.For example, the fifth tertiary blade (22E) is shown having a tungstencarbide insert (36) disposed on the front portion of the bit face (16),and a tungsten carbide insert (38) disposed along the side of the bitface (16). It should be understood that the specific number andplacement of cutting elements on the tertiary blades (22A, 22B, 22C,22D, 22E, 22F) can vary depending on the desired characteristics of thedrill bit (10). For example, for illustrative purposes, FIG. 2 depictsthe third and sixth tertiary blades (22C, 22F) having three tungstencarbide inserts thereon, while the other tertiary blades (22A, 22B, 22D,22E) are shown having two tungsten carbide inserts thereon.Additionally, while the depicted embodiment of the drill bit (10) lacksany polycrystalline diamond compact cutting elements on the tertiaryblades (22A, 22B, 22C, 22D, 22E, 22F), in other embodiments, the lengthof the tertiary blades (22A, 22B, 22C, 22D, 22E, 22F) can be longerand/or the inner portion of the tertiary blades (22A, 22B, 22C, 22D,22E, 22F) can include polycrystalline diamond compact cutters.

The depicted drill bit (10) is further shown having a plurality of jets,ports, and or nozzles, oriented to wash the blades and/or cuttingelements, of which a jet (40) is labeled for reference. A port nozzle(42) is shown at the approximate center of the bit face (16), and isfurther usable for washing the cutters and/or blades, circulating fluid,and/or engaging the formation or various objects. In an embodiment, theinner portion of the bit face (16) can include a recessed conical region(44). For example, FIGS. 1 through 3 depict the bit face (16) having arecessed conical region (44) with an apex at the approximate center ofthe bit face (16). While the depth/height of the recessed conical region(44) can vary depending on the nature of the drill bit, in anembodiment, the recessed conical region (44) can have a height ofapproximately four inches.

Referring now to FIG. 3, a perspective view of the drill bit (10) ofFIG. 1 is shown. As described previously, the depicted drill bit (10)includes a body (12), shank (14), and bit face (16). The bit face (16)is shown having a plurality of primary blades, of which a primary blade(18) is labeled for reference, the primary blade (18) including one ormore tungsten carbide inserts (24) disposed on the front portion of thebit face (16), one or more tungsten carbide inserts (26) disposed on theside of the bit face (16), and one or more polycrystalline diamondcompact cutting elements (28) disposed on the inner portion of theprimary blade (18). The bit face (16) is further shown having aplurality of secondary blades, of which a secondary blade (20) islabeled for reference. The secondary blade (20) is shown having one ormore tungsten carbide inserts (30) disposed on the front of the bit face(16), one or more tungsten carbide inserts (32) disposed on the side ofthe bit face (16), and one or more polycrystalline diamond compactcutting elements (34) disposed on the inner portion of the secondaryblade (20). The bit face (16) is additionally shown having a pluralityof tertiary blades, of which a tertiary blade (22) is labeled forreference. The tertiary blade (22) is shown having one or more tungstencarbide inserts (36) disposed on the front portion of the bit face (16),and one or more tungsten carbide inserts (38) disposed on the side ofthe bit face (16).

In use, the depicted drill bit (10) can be run into a borehole (e.g.,through attachment to a string of drill pipe or a similar conduit and/orconveyance), typically at a time when it is desirable to form a curvedportion of the borehole. Once positioned at a point where drillingoperations are to be performed, the drill bit can be actuated such thatthe cutting elements thereof rotate relative to the formation. Whenboring in a generally straight (e.g, linear) direction, the plurality oftungsten carbide inserts disposed at the outer portion of the bit facewill contact the formation prior to the polycrystalline diamond compactcutting elements, and can crush the formation to form limited cutstherein, while a portion of the formation in front of the bit face thatis not contacted by the tungsten carbide inserts (e.g., a “stump”)enters the recessed conical portion of the bit face to provide stabilitythereto and maintain the direction of the drill bit. The polycrystallinediamond compact cutting elements would then bore through the stump asthe drill bit progressed through the formation.

When boring along a curved path (e.g., when building a curve in aborehole), the drill bit can be urged in a lateral direction at a ratethat will cause turning and/or reorientation of the drill bit at adesired angular rate of change (e.g., through selection of a lateralforce corresponding to the desired angle of the curve). The tungstencarbide insert cutting elements, disposed along the outer portion (e.g.,perimeter and side portions) of the bit face and oriented to crush theformation in a direction perpendicular to the bit face (e.g., outwardfrom the front portion thereof), will remove the formation in a mannerthat allows the drill bit to turn sharply. Portions of the formation,not contacted by the tungsten carbide inserts along the outer portion ofthe bit face (e.g., formation that enters the recessed conical region),will be removed by the polycrystalline diamond compact cutting elements,which displace such portions of the formation in a direction generallyparallel to the bit face.

Embodiments usable within the scope of the present disclosure therebyprovide drill bits and methods capable of rapidly building a curve inborehole, during a single trip, having a faster rate of penetration thanconventional drill bits and methods, and capable of forming curves anangle greater than conventional drill bits and methods, thus shorteningthe length of a curved portion of a borehole as well as the timerequired to build the curve.

While various embodiments usable within the scope of the presentdisclosure have been described with emphasis, it should be understoodthat within the scope of the appended claims, the present invention canbe practiced other than as specifically described herein.

What is claimed is:
 1. A drill bit adapted for forming a curved portionof a borehole, the drill bit comprising: a body having a first end and asecond end; a shank disposed at the first end of the body, wherein theshank is adapted for attachment to a drill string, a downhole component,or combinations thereof; a bit face disposed at the second end of thebody, wherein the bit face comprises a perimeter region and an interiorregion, and wherein the interior region comprises a recessed conicalportion for contacting a formation to provide stability to the drillbit; a plurality of tungsten carbide inserts disposed in the perimeterregion, wherein the plurality of tungsten carbide inserts define aleading edge oriented to bore into the formation in a directiongenerally perpendicular to the bit face; and a plurality ofpolycrystalline diamond compact cutting elements disposed in theinterior region, wherein the plurality of polycrystalline diamondcompact cutting elements are oriented to bore into the formation in adirection generally parallel to the bit face, wherein the plurality oftungsten carbide inserts are adapted to engage the formation to form acurved region of a borehole, and wherein the plurality ofpolycrystalline diamond compact cutting elements are adapted to engagethe formation to form a linear region of the borehole.
 2. The drill bitof claim 1, wherein the recessed conical portion comprises a height offour inches or less.
 3. The drill bit of claim 1, wherein the recessedconical portion comprises a height of four inches or greater.
 4. Thedrill bit of claim 1, wherein the plurality of polycrystalline diamondcompact cutting elements forms a first cut in the formation having afirst dimension, and wherein the plurality of tungsten carbide insertsforms a second cut in the formation having a second dimension less thanthe first dimension for facilitating boring of the drill bit along acurved path.
 5. The drill bit of claim 1, wherein the body comprises anoverall length of five inches or less.
 6. The drill bit of claim 1,wherein the bit face comprises a plurality of blades extendingtherefrom, wherein the plurality of polycrystalline diamond compactcutting elements are positioned along an inner portion of the pluralityof blades, and wherein the plurality of tungsten carbide inserts arepositioned along an outer portion of the plurality of blades, betweenindividual blades of the plurality of blades, or combinations thereof.7. The drill bit of claim 1, further comprising a port positioned at acenter of the bit face for washing the plurality of tungsten carbideinserts, the plurality of polycrystalline diamond compact cuttingelements, or combinations thereof.
 8. A method for forming a borehole,the method comprising the steps of: providing a drill bit into aborehole, wherein the drill bit comprises a bit face having a firstplurality of cutters disposed on an outer portion thereof to define aleading edge and a second plurality of cutters disposed on an innerportion thereof; and forming a curved portion of the borehole by usingthe first plurality of cutters to bore through a formation in adirection generally perpendicular to the bit face while urging the drillbit along a curved path.
 9. The method of claim 8, further comprisingthe step of forming a linear portion of the borehole by using the secondplurality of cutters to bore through a formation in a directiongenerally parallel to the bit face while urging the drill bit along alinear path.
 10. The method of claim 9, wherein the inner portion of thebit face comprises a recessed cone, a recessed dome, or combinationsthereof, and wherein the step of forming the linear portion of theborehole comprises stabilizing the drill bit by moving the drill bitsuch that a portion of the formation enters the recessed cone, recesseddome, or combinations thereof to contact the bit face.
 11. The method ofclaim 9, wherein the first plurality of cutters comprise a plurality oftungsten carbide inserts, wherein the second plurality of cutterscomprise a plurality of polycrystalline diamond compact cuttingelements, wherein the step of forming the curved portion of the boreholecomprises removing portions of the formation with the first plurality ofcutters that comprise a dimension less than that of portions of theformation removed using the second plurality of cutters to facilitatemovement of the drill bit along the curved path.
 12. The method of claim8, wherein the step of forming the curved portion of the boreholecomprises providing the curved portion with an angular rate of changingranging from eight degrees to thirty five degrees per one hundred feetof length.
 13. A drill bit comprising: a bit face having an outerportion and an inner portion; a first plurality of cutters disposed onthe outer portion, wherein the first plurality of cutters are orientedto bore into a formation in a direction generally perpendicular to thebit face; and a second plurality of cutters disposed on the innerportion, wherein the second plurality of cutters are oriented to boreinto a formation in a direction generally parallel to the bit face,wherein the first plurality of cutters are adapted to engage theformation to form a curved region of a borehole, and wherein the secondplurality of cutters are adapted to engage the formation to form alinear region of the borehole.
 14. The drill bit of claim 13, whereinthe inner portion comprises a recessed region having a height of fourinches or less.
 15. The drill bit of claim 13, wherein the inner portioncomprises a recessed region having a height of four inches or greater.16. The drill bit of claim 13, wherein the first plurality of cutterscomprises a plurality of tungsten carbide inserts that define a leadingedge that contacts the formation prior to the second plurality ofcutters, wherein the leading edge adapted to crush the formation whenforming a curved region of the borehole.
 17. The drill bit of claim 16,wherein the second plurality of cutters comprise a plurality ofpolycrystalline diamond compact cutting elements adapted to cut theformation.
 18. The drill bit of claim 13, further comprising a portpositioned at a center of the bit face for washing the first pluralityof cutters, the second plurality of cutters, or combinations thereof.19. The drill bit of claim 17, wherein the plurality of polycrystallinediamond compact cutting elements forms a first cut in the formationhaving a first dimension, and wherein the plurality of tungsten carbideinserts forms a second cut in the formation having a second dimensionless than the first dimension for facilitating boring of the drill bitalong a curved path.
 20. The drill bit of claim 13, wherein the drillbit comprises an overall length of five inches or less.
 21. The drillbit of claim 13, wherein the bit face comprises a plurality of bladesextending therefrom, wherein the second plurality of cutters arepositioned along an inner portion of the plurality of blades, andwherein the first plurality of cutters are positioned along an outerportion of the plurality of blades, between individual blades of theplurality of blades, or combinations thereof.